Production and treatment of artificial filamentary materials



July 21, 1959 I R. J. BROWN ETAL 2,395,790

PRODUCTION AND TREATMENT OF ARTIFICIAL FILAMENTARY MATERIALS Filed April 4, 1955 United States Patent 2,895,790 Patented July 21, 1959 ice PRODUCTION AND TREATMENT OF ARTIFICIAL FIL-AMENTARY MATERIALS Russell Jacques Brown and John Downing, Spondon, near Derby, England, assignors to British Celanese Limited, a corporation of Great Britain Application April 4, 1955, Serial No. 499,166

Claims priority, application Great Britain April 12, 1954 6 Claims. (Cl. 18-54) This invention relates to the production and treatment of artificial filamentary materials, and especially to their manufacture by wet spinning processes.

In United States applications Ser. Nos. 323,788, filed December 3, 1952; 451,191, filed August 20, 1953, and 488,868, filed February 17, 1955, there are described wet-spinning processes and apparatus in which the filaments formed travel in the same direction as a coagulating liquid up a narrow tube, and are drawn upwardly from the open end of the tube. Usually the filaments are still slightly separated when they leave the tube, though they come together at or before they reach the drawing means; for the purpose of the present specification the filaments at all points after leaving the tube will be referred to collectively as a yarn, Whether or not they are already in contact.

While in such processes the greater part of the coagulating liquid overflows at the top of the tube, where it may be collected and drawn-01f in any suitable way, a substantial proportion may be carried up to a considerable height by the travelling yarn unless some means for preventing this is adopted. This phenomenon is indeed observed in any process in which a yarn is drawn fairly rapidly upwards out of a narrow tube containing a liquid, especially when the individual filaments do not actually come together until after they have left the tube. The tension imparted to the yarn by the weight of the liquid carried up may have an adverse effect on its textile properties.

One Way of removing a considerable part of the liquid from the yarn and so preventing the yarn from carrying up a large weight of the liquid is to fix a yarn guide or the like directly above the open end of the tube to wipe liquid off the yarn, but we have found that this also can be undesirable in that it tends to increase the number of broken filaments in the yarn.

US. application Ser. No. 217,816, now Patent No. 2,786,737, filed March 27, 1951, describes a device comprising a pulley set skew with respect to the plane of the yarn, over which the yarn passes after leaving the tube; this pulley has the efiect of inserting a false twist in the yarn by virtue of which the amount of liquid carried up is very much reduced. However, the insertion of this false twist is not always desirable.

US. application Ser. No. 451,190, filed August 20, 1954, describes passing the yarn, after it has left the narrow tube, through a stripping device which preferably comprises an inverted funnel, by means of which liquid wiped off from the yarn can be directed clear of the upper end of the tube. US. application Ser. No. 457,721, now Patent No. 2,852,808, filed September 22, 1954, describes the use of a conical wire spiral for the same purpose. The present invention describes another method and device, which have been found to be par ticularly effective in removing liquid from the yarn and by means of which the liquid removed is directed away from the upper end of the narrow tube in the form of a compact stream which is easily collected.

According to the invention, a process in which filamentary material passes up and out of :a substantially vertical narrow tube up which liquid is also flowing, especially a wet spinning process for the production of artificial textile material, comprises the step of causing the material, after it has left the tube and before it makes contact with any other object, to pass in an arc of a circle over a rotating stripping roller. Preferably the material passes in contact with the stripping roller over an arc of 590, and especially 10-70.

The stripping roller may be positively driven or it may be freely mounted and caused to rotate by the friction of the filamentary material passing in contact with it. Its peripheral speed preferably does not exceed the rate of travel of the filamentary material in contact with it, and it may with advantage be slightly or even considerably lower. Thus the peripheral speed of the roller may be between about 60% and 98% of the rate of travel of the filaments. Generally speaking, with yarns of low or moderate denier, say up to about 500, the peripheral speed of the roller may be only slightly below the rate of travel of the yarn, i.e. between about 90 and 98% of the said rate, while with heavy denier material such as tow it may be lower. A freely mounted roller may be lightly braked in order to maintain its peripheral speed below the rate of travel of the filamentary material.

The invention includes also apparatus for making filamentary material by a wet-spinning process, which comprises a substantially vertical spinning vessel including a vertical tube of small diameter up which both the filaments formed and a coagulating liquid travel, means for extruding a spinning solution in the form of filaments into a coagulating liquid in the said spinning Vessel, means for drawing the filaments produced upwardly through and out of the said vertical tube, and between the said drawing means and the upper end of the vertical tube, a positively driven or freely mounted stripping roller positioned so that the filamentary material passes over it in an arc of a circle extending preferably over an angle between 5 and 90 and especially between 10 and The stripping roller may be made of any suitable hard material which is not attacked by the liquid adhering to the filamentary material, for instance stainless steel, Phosphor bronze, glass or a suitable synthetic resin. When a heavy roller, e.g. a bronze roller, is used, it is best that it should be positively driven. The surface of the roller is preferably smooth and strictly cylindrical. Its diameter may for example be between about 2 and 8 inches.

Not only does the stripping roller effectively remove from the filamentary material a high proportion of the liquid carried up by it, but it does so in such a way that all or nearly all the liquid removed falls back in the form of a compact stream at a considerable angle to the vertical; thus the liquid removed from the yarn is directed away from the upper end of the narrow tube, and can be collected by means placed well clear of the path of the yarn between the narrow tube and the stripping roller. It is very surprising that at least the bulk of the liquid removed from the yarn by the stripping roller is neither flung off from the roller by centrifugal force, nor falls vertically back down the yarn, but falls back in a compact and easily collected stream at an angle to the vertical.

The means for drawing the yarn from the narrow tube may for example be a godet in the form of a cylindrical roller, provided if desired with a skew idler roller or other means for keeping separate the turns made by the filamentary material passing round the godet, or it may comprise a fluted roller or the like as described in US. application Serial No. 451,193, filed August 20, 1954, or a set of pegs or bars arranged in the form of a cylinder as described in US. application Ser. No. 451,192, filed August 20, 1954.

After leaving the godet the yarn is advantageously washed until it is free or nearly free from the coagulating liquid, for example by means of a washing device such as is described in U.S. applications Ser. Nos. 323,788 and 457,684, filed September 22, 1954. We have however found that it is easier to reduce the amount of coagulating liquid left in the yarn to a very low figure if between the godet and the washing device the yarn is subjected to a light friction or wiping action by means of which part of the liquid still adhering to the yarn is removed. Preferably such friction is applied to the yarn from two or more different directions successively. Thus we have found it very advantageous to pass the yarn in a slightly zig-zag path between a number of smooth fingers or like members arranged to make contact with opposite sides of the yarn alternately. The axes of the several fingers may all be in the same plane, but are preferably slightly off-set with respect to each other so as to reduce the amount by which a yarn passing between them deviates from a straight line. We may for example employ 4-8 fingers, spaced between about 0.5 and 1.0 inch apart. It is believed that the effectiveness of this simple device is due in part to a flattening and splaying out of the multi-filament yarn as it passes in contact with the fingers, so that all the individual filaments make contact with the friction members. A friction device of this kind may be employed between the godet and the washing device whatever means are adopted to remove adherent liquid before the yarn reaches the godet, or indeed even if no such means are provided.

The invention is illustrated by the accompanying drawing, which shows diagrammatically and in section a wetspinning apparatus in which both a stripping roller and a friction device as described above are employed.

Referring now to the drawing, the wet spinning apparatus comprises a spinning vessel 1, a stripping roller 2, a godet 3 with an associated skew idler roller 4, and a set of friction fingers 5. The spinning vessel 1 comprises an extrusion chamber 6, from the top of which leads a setting tube 7 of much smaller diameter. The setting tube 7 consists of a lower section 8 opening into the extrusion chamber 6 and having its lower end flared, and an upper section 9 of somewhat smaller diameter than the lower section 8, and terminating at its upper end in an orifice 10 of smaller diameter still.

A spinning jet 11, provided with a feed pipe 12, is mounted axially in the extrusion chamber 6 directly below and about 2-3 inches from the flared lower end of the lower section 8 of the setting tube. Inlets 13 for liquid lead into the bottom of the extrusion chamber 6, and a fine wire gauze 14 extends across the chamber at a level below that of the jet 11.

A collector head 15, provided with a run-off 16 for liquid, is mounted at the upper end of the upper section 9 of the setting tube, and extends well above and well below the level of the orifice 10. A supporting fin 17 attached to the wall of the collector head 15 carries a guide member 18 comprising an upper section 19 inclined upwardly towards the line followed by a yarn travelling from the orifice 10 vertically upwards to the stripping roller 3, and a vertical lower section 20 which extends into the collector head 16 to a level below that of the orifice 10.

The stripping roller 2 is either a smooth cylindrical Phosphor bronze roller provided with driving means (not shown) by means of which it can be driven at a peripheral speed bearing any desired ratio between .621 and 1:1 to that of the godet 3, or a light freely running roller, which may if desired be slightly braked by any conventional means.

The godet 3 is so placed with respect to the axis of the setting tube 7 and the stripping roller 2 that yarn passing from the orifice 10 to the godet 3 makes contact with the stripping roller over an arc of about 45 -50.

The friction fingers are identical smooth cylindrical members arranged parallel to one another and in two parallel planes spaced apart by about half the diameter of the members.

In operation, a coagulating liquid is fed through the inlets 13 into the extrusion chamber 6, and flows through the gauze 14, which serves to eliminate turbulence or at least reduce it to a minimum, past the jet 11, and into and up the setting tube 7, at the top of which it overflows into the collector head 15 which it leaves by the run-off 16. Spinning solution is pumped at a constant rate of flow through the feed pipe 12 to the spinning jet 11, and the filaments formed travel up the setting tube 7 in which they are coagulated. Information about suitable rates of flow for the coagulating liquid in relation to the speed at which the filaments leave the setting tube 7 will be found in U.S. applications Ser. Nos. 323,788 and 451,191.

From the orifice 10 at the upper end of the setting tube the filaments, now in the form of a yarn 21, pass over the stripping roller 2 to the godet 3, by means of which they are drawn up and out of the setting tube. As the yarn passes over the stripping roller 2 much of the coagulating liquid carried up by it is transferred from the yarn to the roller, from which it falls off in a compact stream onto the upper section 19 of the guide member 18; the liquid then flows down the guide member until it enters the collector head 16 at a level at which it does not cause any disturbance in the liquid actually leaving the setting tube 7.

The godet 3 runs at such a rate that the filaments, before they are fully set, undergo a substantial degree of stretch. From the godet the yarn passes in a zigzag path over and under alternate members of the set of friction fingers 5, where it loses more coagulating liquid. It is then passed to a washing device (not shown) of any suitable kind. After being well washed the yarn is wound up, if desired after being dried.

' The new method and apparatus are found to be particularly well adapted for use in wet-spinning processes in which a cellulose acetate filamentary material is set by means of a coagulant comprising aqueous diethylene glycol diacetate', such processes are described in U.S. applications Ser. Nos. 323,788, 451,191, 451,193, 457,684, 451,192 and 488,868. The invention is however also applicable to other wet-spinning processes, especially to processes in which an acetone solution of cellulose acetate is extruded into aqueous acetone, and to processes in which an acetic acid solution of cellulose acetate is extruded into aqueous acetic acid which may contain in solution a high concentration of a salt, e.g. an alkali metal acetate. Acetic acid spinning solutions of cellulose acetate may be primary or secondary acetylation solutions in which the catalyst has been neutralised, and if necessary the concentration 'of cellulose acetate adjusted, as by 'theaddition of further acetic acid, to give the solution a suitable spinning viscosity. The invention is of particular value in the production of' yarns of heavy denier, such as are suited for cutting into staple fibre, or for combining to form a tow which is to be cut into staple fibre. Such yarns may for example contain 1000 or more individual filaments.

- Having described our invention what we desire to secure by Letters Patent is:

1. A process in which filamentary material is drawn up and out of a substantially vertical narrow zone up which liquid is also flowing and in which a drawing force is applied to said filamentary material after said filamentary material has left said liquid which comprises subjecting the material between the point at which it leaves the vertical narrow zone and that at which the drawing force is applied to a change of direction of l0-70 over an arc of a circle caused by contact with a smooth cylindrical solid surface of diameter 2-8 inches moving at a speed between 60 and 98% of that of the material whereby liquid is moved from the material and caused to fall back as a compact stream at an angle to the vertical and collecting said compact stream at a collection zone which is below the first point of contact of said filamentary material and said surface said collection zone being displaced from said filamentary material and being on the side of said filamentary material engaged by said surface.

2. A process for the production of artificial filamentary material by a wet spinning process in which the material passes up and out of a substantially vertical narrow zone up which a coagulating liquid is also flowing and in which a drawing force is applied to said filamentary material after said filamentary material has left said liquid, which comprises subjecting the material between the point at which it leaves the vertical narrow zone and that at which the drawing force is applied to a change of direction of -70 over an arc of a circle caused by contact with a smooth cylindrical solid surface of diameter 2-8 inches moving at a speed between 60 and 98% of that of the material whereby coagulating liquid is removed from the material and caused to fall back as a compact stream at an angle to the vertical and collecting said compact stream at a collection zone which is below the first point of contact of said filamentary material and said surface, said collection zone being displaced from said filamentary material and being on the side of said filamentary material engaged by said surface.

3. Process according to claim 2, wherein filamentary material of denier below 500 is formed, and the solid surface moves at a speed between and 98% of that of the yarn.

4. Process according to claim 3, wherein the solid surface is set and maintained in motion solely by the passage of the filamentary material in contact with it.

5. Process according to claim 3, wherein the solid surface is set and maintained in motion independently of the passage of the filamentary material.

6. Process according to claim 2, wherein beyond the point at which the drawing force is applied to it the material is subjected to light friction from at least two directions successively, and is subsequently washed.

References Cited in the file of this patent UNITED STATES PATENTS 827,434 Friedrich July 31, 1906 2,182,768 Uytenbogaart Dec. 5, 1939 2,705,183 James Mar. 29, 1944 2,536,093 Coleman Jan. 2, 1951 2,642,333 Tomonari June 16, 1953 2,700,794 Taylor Feb. 1, 1955 2,711,559 Lynch June 28, 1955 FOREIGN PATENTS 738,054 France Dec. 20, 1932 742,817 Germany Dec. 11, 1943 287,553 Great Britain Aug. 6, 1929 695,559 Great Britain Aug. 12, 1953 

1. A PROCESS IN WHICH FILAMENTARY MATERIAL IS DRAWN UP AND OUT OF A SUBSTANTIALLY VERTICAL NARROW ZONE UP WHICH LIQUID IS ALSO FLOWING AND IN WHICH A DRAWING FORCE IS APPLIED TO SAID FILAMENTARY MTERIAL AFTER SAID FLAMENTARY MATERIAL HAS LEFT SAID LIQUID WHICH COMPRISES SUBJECTING THE MATERIAL BETWEEN THE POINT AT WHICH IT LEAVES THE VERTICAL NARROW ZONE AND THAT AT WHICH THE DRAWING FORCE IS APPLIED TO A CHANGE OF DIRECTION OF 10-70* OVER AN ARCE OF A CIRCLE CAUSED BY CONTACT WITH A SMOOTH CYLINDRICAL SOLID SURFACE OF DIAMETER 2-8 INCHES MOVING AT A SPEED BETWEEN 60 AND 98% OF THAT OF THE MATERIAL WHEREBY LIQUID IS MOVED FROM THE MATERIAL AND CAUSED TO FALL BACK AS A COMPACT STREAM AT AN ANGLE THE VERTICAL AND COLLECTING SAID COMPACT STREAM AT A COLLECTION ZONE WHICH IS BELOW THE FIRST POINT OF CONTACT 